﻿#pragma once

namespace fast_io
{

namespace details
{

enum class crc32_option
{
	crc32,
	crc32c
};

inline constexpr void crc32_to_byte_ptr_commom_impl(::std::uint_least32_t crc, ::std::byte *ptr) noexcept
{
	crc = ~crc;
	if constexpr (::std::endian::big != ::std::endian::native)
	{
		crc = ::fast_io::byte_swap(crc);
	}
#if (__cpp_if_consteval >= 202106L || __cpp_lib_is_constant_evaluated >= 201811L) && __cpp_lib_bit_cast >= 201806L
#if __cpp_if_consteval >= 202106L
	if consteval
#elif __cpp_lib_is_constant_evaluated >= 201811L
	if (__builtin_is_constant_evaluated())
#endif
	{
		auto a{::std::bit_cast<::fast_io::freestanding::array<::std::byte, sizeof(::std::uint_least32_t)>>(crc)};
		::fast_io::freestanding::nonoverlapped_bytes_copy_n(a.data(), a.size(), ptr);
	}
	else
#endif
	{
		::fast_io::freestanding::nonoverlapped_bytes_copy_n(
			reinterpret_cast<::std::byte const *>(__builtin_addressof(crc)), sizeof(::std::uint_least32_t), ptr);
	}
}

inline constexpr ::std::uint_least32_t calculate_crc32_common(::std::uint_least32_t crc, ::std::byte const *i,
															  ::std::byte const *ed,
															  ::std::uint_least32_t const *crctb) noexcept
{
	for (; i != ed; ++i)
	{
		crc = crctb[(static_cast<::std::uint_least32_t>(*i) ^ crc) & 0xff] ^ (crc >> 8);
	}
	return crc;
}
// clang-format off
inline constexpr ::std::uint_least32_t crc32_tb[256]{
    0x0,        0x77073096, 0xee0e612c, 0x990951ba, 0x76dc419,  0x706af48f, 0xe963a535, 0x9e6495a3, 0xedb8832,
    0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x9b64c2b,  0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2,
    0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a,
    0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172,
    0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
    0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423,
    0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab,
    0xb6662d3d, 0x76dc4190, 0x1db7106,  0x98d220bc, 0xefd5102a, 0x71b18589, 0x6b6b51f,  0x9fbfe4a5, 0xe8b8d433,
    0x7807c9a2, 0xf00f934,  0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x86d3d2d,  0x91646c97, 0xe6635c01, 0x6b6b51f4,
    0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
    0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074,
    0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0,
    0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525,
    0x206f85b3, 0xb966d409, 0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81,
    0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x3b6e20c,  0x74b1d29a, 0xead54739, 0x9dd277af, 0x4db2615,
    0x73dc1683, 0xe3630b12, 0x94643b84, 0xd6d6a3e,  0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0xa00ae27,  0x7d079eb1,
    0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76,
    0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e,
    0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, 0x36034af6,
    0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
    0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7,
    0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x26d930a,  0x9c0906a9, 0xeb0e363f,
    0x72076785, 0x5005713,  0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0xcb61b38,  0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7,
    0xbdbdf21,  0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777,
    0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
    0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc,
    0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330,
    0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94,
    0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d};

inline constexpr ::std::uint_least32_t crc32c_tb[256]{
    0x0,        0xf26b8303, 0xe13b70f7, 0x1350f3f4, 0xc79a971f, 0x35f1141c, 0x26a1e7e8, 0xd4ca64eb, 0x8ad958cf,
    0x78b2dbcc, 0x6be22838, 0x9989ab3b, 0x4d43cfd0, 0xbf284cd3, 0xac78bf27, 0x5e133c24, 0x105ec76f, 0xe235446c,
    0xf165b798, 0x30e349b,  0xd7c45070, 0x25afd373, 0x36ff2087, 0xc494a384, 0x9a879fa0, 0x68ec1ca3, 0x7bbcef57,
    0x89d76c54, 0x5d1d08bf, 0xaf768bbc, 0xbc267848, 0x4e4dfb4b, 0x20bd8ede, 0xd2d60ddd, 0xc186fe29, 0x33ed7d2a,
    0xe72719c1, 0x154c9ac2, 0x61c6936,  0xf477ea35, 0xaa64d611, 0x580f5512, 0x4b5fa6e6, 0xb93425e5, 0x6dfe410e,
    0x9f95c20d, 0x8cc531f9, 0x7eaeb2fa, 0x30e349b1, 0xc288cab2, 0xd1d83946, 0x23b3ba45, 0xf779deae, 0x5125dad,
    0x1642ae59, 0xe4292d5a, 0xba3a117e, 0x4851927d, 0x5b016189, 0xa96ae28a, 0x7da08661, 0x8fcb0562, 0x9c9bf696,
    0x6ef07595, 0x417b1dbc, 0xb3109ebf, 0xa0406d4b, 0x522bee48, 0x86e18aa3, 0x748a09a0, 0x67dafa54, 0x95b17957,
    0xcba24573, 0x39c9c670, 0x2a993584, 0xd8f2b687, 0xc38d26c,  0xfe53516f, 0xed03a29b, 0x1f682198, 0x5125dad3,
    0xa34e59d0, 0xb01eaa24, 0x42752927, 0x96bf4dcc, 0x64d4cecf, 0x77843d3b, 0x85efbe38, 0xdbfc821c, 0x2997011f,
    0x3ac7f2eb, 0xc8ac71e8, 0x1c661503, 0xee0d9600, 0xfd5d65f4, 0xf36e6f7,  0x61c69362, 0x93ad1061, 0x80fde395,
    0x72966096, 0xa65c047d, 0x5437877e, 0x4767748a, 0xb50cf789, 0xeb1fcbad, 0x197448ae, 0xa24bb5a,  0xf84f3859,
    0x2c855cb2, 0xdeeedfb1, 0xcdbe2c45, 0x3fd5af46, 0x7198540d, 0x83f3d70e, 0x90a324fa, 0x62c8a7f9, 0xb602c312,
    0x44694011, 0x5739b3e5, 0xa55230e6, 0xfb410cc2, 0x92a8fc1,  0x1a7a7c35, 0xe811ff36, 0x3cdb9bdd, 0xceb018de,
    0xdde0eb2a, 0x2f8b6829, 0x82f63b78, 0x709db87b, 0x63cd4b8f, 0x91a6c88c, 0x456cac67, 0xb7072f64, 0xa457dc90,
    0x563c5f93, 0x82f63b7,  0xfa44e0b4, 0xe9141340, 0x1b7f9043, 0xcfb5f4a8, 0x3dde77ab, 0x2e8e845f, 0xdce5075c,
    0x92a8fc17, 0x60c37f14, 0x73938ce0, 0x81f80fe3, 0x55326b08, 0xa759e80b, 0xb4091bff, 0x466298fc, 0x1871a4d8,
    0xea1a27db, 0xf94ad42f, 0xb21572c,  0xdfeb33c7, 0x2d80b0c4, 0x3ed04330, 0xccbbc033, 0xa24bb5a6, 0x502036a5,
    0x4370c551, 0xb11b4652, 0x65d122b9, 0x97baa1ba, 0x84ea524e, 0x7681d14d, 0x2892ed69, 0xdaf96e6a, 0xc9a99d9e,
    0x3bc21e9d, 0xef087a76, 0x1d63f975, 0xe330a81,  0xfc588982, 0xb21572c9, 0x407ef1ca, 0x532e023e, 0xa145813d,
    0x758fe5d6, 0x87e466d5, 0x94b49521, 0x66df1622, 0x38cc2a06, 0xcaa7a905, 0xd9f75af1, 0x2b9cd9f2, 0xff56bd19,
    0xd3d3e1a,  0x1e6dcdee, 0xec064eed, 0xc38d26c4, 0x31e6a5c7, 0x22b65633, 0xd0ddd530, 0x417b1db,  0xf67c32d8,
    0xe52cc12c, 0x1747422f, 0x49547e0b, 0xbb3ffd08, 0xa86f0efc, 0x5a048dff, 0x8ecee914, 0x7ca56a17, 0x6ff599e3,
    0x9d9e1ae0, 0xd3d3e1ab, 0x21b862a8, 0x32e8915c, 0xc083125f, 0x144976b4, 0xe622f5b7, 0xf5720643, 0x7198540,
    0x590ab964, 0xab613a67, 0xb831c993, 0x4a5a4a90, 0x9e902e7b, 0x6cfbad78, 0x7fab5e8c, 0x8dc0dd8f, 0xe330a81a,
    0x115b2b19, 0x20bd8ed,  0xf0605bee, 0x24aa3f05, 0xd6c1bc06, 0xc5914ff2, 0x37faccf1, 0x69e9f0d5, 0x9b8273d6,
    0x88d28022, 0x7ab90321, 0xae7367ca, 0x5c18e4c9, 0x4f48173d, 0xbd23943e, 0xf36e6f75, 0x105ec76,  0x12551f82,
    0xe03e9c81, 0x34f4f86a, 0xc69f7b69, 0xd5cf889d, 0x27a40b9e, 0x79b737ba, 0x8bdcb4b9, 0x988c474d, 0x6ae7c44e,
    0xbe2da0a5, 0x4c4623a6, 0x5f16d052, 0xad7d5351};
// clang-format on
template <crc32_option opt>
inline constexpr ::std::uint_least32_t calculate_crc32(::std::uint_least32_t crc, ::std::byte const *i,
													   ::std::byte const *ed) noexcept
{
	if constexpr (opt == crc32_option::crc32)
	{
		return calculate_crc32_common(crc, i, ed, crc32_tb);
	}
	else
	{
		return calculate_crc32_common(crc, i, ed, crc32c_tb);
	}
}

template <crc32_option opt>
class basic_crc32_scalar_context
{
	::std::uint_least32_t crcv{0xffffffff};

public:
	static inline constexpr ::std::size_t digest_size{sizeof(::std::uint_least32_t)};
	inline constexpr void update(::std::byte const *first, ::std::byte const *last) noexcept
	{
		crcv = calculate_crc32<opt>(crcv, first, last);
	}
	inline constexpr void reset() noexcept
	{
		crcv = 0xffffffff;
	}
	inline constexpr ::std::uint_least32_t digest_value() const noexcept
	{
		return ~crcv;
	}
	inline constexpr void do_final() const noexcept
	{}
	inline constexpr void digest_to_byte_ptr(::std::byte *ptr) const noexcept
	{
		::fast_io::details::crc32_to_byte_ptr_commom_impl(crcv, ptr);
	}
};
} // namespace details

using crc32_context = ::fast_io::details::basic_crc32_scalar_context<::fast_io::details::crc32_option::crc32>;
using crc32c_context = ::fast_io::details::basic_crc32_scalar_context<::fast_io::details::crc32_option::crc32c>;

} // namespace fast_io
